Formation of a head and neck region in humans is an extremely complex process, which requires precise orchestration of many different types of tissues and cells (skeleton, muscles, brain, etc). This process is so complicated and sensitive that genetic mistakes often lead to various types of cranial malformations. In fact, at least over a third of genetic problems in humans have associated malformations of head structures, often hard tissues, such as bones and cartilages. These abnormal situations can range from relatively mild to very severe and are often characterized by presence of various types of cancers as well suggesting disruption of basic process of cell proliferation/division and cell differentiation. Recent studies suggest an important role for a relatively novel group of genes, called microRNAs, in embryonic development. We found evidence for an important role of microRNAs (miRNAs) in cranial intramembranous bone development and we hypothesize that these molecules will be important to understand craniofacial hard tissue abnormalities and cancers. Here we wish to reveal the exact functions of craniofacial tissues-specific miRNAs in isolated cranial skeletal cells (in vitro) and in cranial skeletal structures of the developing embryos (in vivo). RELEVANCE Craniofacial abnormalities and syndromes are some of the most common birth defects that are often associated with severe disabilities, cancers, hearing loss, problems related to breathing, eating, and speech. We aim to understand mechanisms of the cranial bone development and morphogenesis in normal and abnormal conditions. In this proposal, we want to investigate the biological roles for several identified cranial dermal bone-specific candidate miRNAs. The results of this analysis will be used to start a more comprehensive examination to establish how miRNAs control intramembranous osteoblast differentiation in normal and diseased tissue. PUBLIC HEALTH RELEVANCE: Each year thousands of children are born with craniofacial diseases related to abnormal cranial bone biology. We recently found that microRNAs, an important class of regulatory molecules, are required for cranial bone formation. We believe that that learning about functions of these molecules using sophisticated genetic and molecular tools will help us understand the mechanisms governing normal cranial bone biology and allow us to develop ways to diagnose, prevent and treat various craniofacial syndromes in the future.